Broken playlist_load_files with mpv v0.38.0 due to changed loadfile arguments

[marco-04]

The current version of mpv changed the loadfile instruction to take these arguments:

loadfile <url> [<flags> [<index> [<options>]]]

(from https://mpv.io/manual/stable/#command-interface-[%3Coptions%3E]]]) where index is a newly added argument.

The current implementation of playlist_load_files is

    pub fn playlist_load_files(&self, files: &[(&str, FileState, Option<&str>)]) -> Result<()> {
        for (i, elem) in files.iter().enumerate() {
            let args = elem.2.unwrap_or("");

            let ret = self.command(
                "loadfile",
                &[&format!("\"{}\"", elem.0), elem.1.val(), args],
            );

            if let Err(err) = ret {
                return Err(Error::Loadfiles {
                    index: i,
                    error: ::std::rc::Rc::new(err),
                });
            }
        }
        Ok(())
    }

and the args variable now takes the place of the new index argument.

(for reference, this was the old specification: https://web.archive.org/web/20240414164307/https://mpv.io/manual/stable/#command-interface-[%3Coptions%3E]])